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<TITLE>Switch -mc&lt;par&gt; - set advanced compression parameters</TITLE>

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<P class="title">Switch <B>-MC&lt;par&gt;</B>
-  set advanced compression parameters<hr></P>

<P>Improper use of this switch may lead to suboptimal performance
and compression. This switch has the following syntax:</P>

<P>-mc[channels][mode][+ or -]</P>

<P>where <I>&lt;mode&gt;</I> is the single character field defining
the compression algorithm to be configured. Possible <I>&lt;mode&gt;</I>
values are:<br>
</P>

<TABLE>

<TR>
<TD><b>D</b></TD>
<TD>delta compression;</TD>
</TR>

<TR>
<TD><b>E</b></TD>
<TD>x86 executable compression;</TD>
</TR>

<TR>
<TD><b>L</b></TD>
<TD>long range search;</TD>
</TR>

<TR>
<TD><b>X</b></TD>
<TD>exhaustive search.</TD>
</TR>
</TABLE>

<P>'+' sign at the end of switch applies the selected algorithm module
to all processed data, '-' disables it completely. If no sign is specified,
WinRAR chooses modules automatically, based on data and current compression
method. Switch -mc- disables all modes.</P>

<P>&lt;<I>Channels&gt;</I> parameter is used by delta compression and ignored
by other modes. Available modes are described below.</P>

<h1><b>Delta compression</b></h1>

<p>Splits data to several single byte channels and calculates the difference
between them. Can improve the compression ratio of table data. &lt;Channels&gt;
is the number of byte channels from 1 to 31.</p>

<h1><b>x86 executable compression</b></h1>

<p>Can improve the compression ratio of 32 and 64 bit x86 executables.</p>


<h1><b>Long range search</b></h1>

<p>Enables the search algorithm designed to efficiently locate longer
and more distant repeated data blocks. It can helps to improve the compression
ratio and sometimes speed for redundant data like big text files.
This algorithm increases memory requirements when archiving, but doesn't
affect extraction memory requirements or speed.</p>

<p>If neither -mcl+ nor -mcl- are specified, RAR applies the long range
search depending on the compression method,
<a href="HELPGetArcGeneral.htm#DictSize">dictionary size</a>
and other parameters. This algorithm is required and enabled automatically
for dictionaries exceeding 4 GB, where it can't be turned off with
-mcl- switch.</p>

<p>Long range search mode is applicable to -m2..-m5 <a href="HELPSwM.htm">
compression methods</a> and ignored for -m1.</p>


<h1><b>Exhaustive search</b></h1>

<p>Enables much slower and more exhaustive repeated data search
and compression algorithm. It might provide the additional compression gain
on text data, but at much lower speed. Long range search is needed to
implement this mode efficiently, so -mcx activates it automatically.</p>

<h1><B>Example</B></h1>

<P>create a solid archive with 1 GB dictionary and exhaustive search</P>

<p class="sample">WinRAR a -s -md1g -mcx texts *.txt</p>
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